Time-measuring apparatus



l -July zo 1926. 1592316 T. AOKI lET' AL 'una 'lumsunma 'Arrm'nus 'una July so. 192:4

Patented July 210, 1926.

UNITED STATES PATENT OFFICE.

TAMOTSU AOKI AND MASUO HIAGIWABA, OIF TOKYO, JAPAN.

TIME-MEASAUING APPARATUS.

'Application led July 30, 1924, Serial No. 789,064, and in Japan February 13, 1924.

This invention relates to improvements in apparatus for accurately measuring very short intervals of time, and has particular reference to an apparatus far measuring the velocity of a projectile etc.

A general method of measuring avery `short time is to employ a known standard time with which the time to be measured is compared and lthese two times, ont known l and the other to be measured, are) recorded in a form of length so that they are easily compared. It is therefore concluded that the accuracy of measurement entirely depends upon the magnitude of lengths recorded b the measuring apparatus.

Trixie obect of the. invention is to obtain records. o very great lengths, or toV magnify the lengths at will, so that a time is measured with an accuracy far better than that in the known apparatus.

In the accompanying drawings.

Fig. 1 is a diagrammatical view 'of the in-v vention applied to the measurement of velocity of a projectile; p Fig. 2 is adetailed plan of a perforated rotating 'drum and its concentric auxiliary drum employed in this invention; and

Fig. 3. is an enlarged sectional View of the main parts of the invention. l

Referring to the drawings, 9 is a drum rotating with a known velocity which is therefore employed as a means for giving the standard time in this invention. This drum is provided with holes or slits in itsl periphery asshown at 8. 10 is a source of ightwhich is arranged on the axial center of the drum. .7 is an arcurate wall or supporter arranged concentric with the rotatmgx drum vand having upon its inner surface a film of sensitized paper to record the imagesof theY slits 8 b the source of light 10. In the example s own, the source of light 10 consists in a discharging gap o1' electric spark. Now, suppose that the drum 9 stands still and the gap is sparked, then the images of the slits 8 will be .formed on the film on the wall 7. When the drum is rotated and the gap isintermittently sparked, an image of `a certain slit will be recorded on the film on the wall by the lirst spark and also another image ofthe same slit by the second spark will be recorded in 'a certain circumferential distance from the first image and so on. This circumferential distance corresponds to V Bv y r again let sfbe the circumferential distance between the first and the second images, on the wall t the corresponding time then fs=v=a r Therefore any desired magnitude of the length of arccan be obtained by properly selecting the ratio Rw, although the value of v will be limited to a certain magnitude by thev strength ofthe material of the drum 9.

In order to distinguish an image of a slit or hole from another, the lengths or the shapes or sides of the slits may be varied. For .the same urpose, the oles or` slits may be arrang in a zigzag way.

Also in order to get clear images on the film .a series of'sets of lenses 13 corresponding to the. number and position of the slitsv 8, may be used by properly lixing them on another drum`2.

One example of carrying into effect of this invention for measuring the velocity of a projectile is shown by Fig. 1. In this figure, 11 is a projectile, in the path X X of which are arranged two discharge gaps 6, 6 of Leyden jars 12, 12 yin parallel and in their common circuit the saidA discharge gap or the source of light 10 1s provided. 1 is a constant s eed electrlc motor, on the rotating shaft o 'which the drum 1 9 and the auxiliary drumY 2 is. fitted. One terminal of discharge gap 10 is supported on .the bearing 3 while the other is fixed to the shaft ofthe motor. 14 is a source of electricity to charge the Leyden jars.

o i's a switch. y

In operation, the motor l is rotated. The switch 5 is closed to charge the Leyden jars and then again opened. Then the fire arm is fired. When the projectile passes through the first gap 6, the gap 1Q is sparked, and similarly when it passes through the second gap' 6', the gap 10 is sparked again. Thus, the images of one or more of the slits 8 are twice formed in the iilm on the Wall 7. Let, S be the distance of the iirst and the second images of respective slit along' the arc of the Wall, Lhen the time t required Jfor the projectile in passing from the iirst gap 6 to the second gap 6 isobtained by S tsv.

Induction coils may be used in piace of Leyden jars. ,In this case, so called Wire targets made of easily breakable Wires are conveniently used in place of gaps 6 and 6 and the Wire of each target is connected with primary coil of the induction coil in one end and to electric batteries in theiother. rlfhe secondary coil of the induction coil is connected with the terminals of the gap 10.

When the projectile breaks the Wire targets, the gap 10 is successively sparked.

The experiments by using the above described apparatus may be carried on in a dark chamber. But it is preferably convenient to arrange the parts 2, 7, and 9 in a closed box so that the experiments may he carried on in an open iield.

Claims:

1. An apparatus for measuring a short time, including a drum having slits or holes in its periphery, a source of light at the center of said drum, means to rotate said drum at a predetermined velocity, and a fixed arcuate member concentrically arranged with respect to said drum and to which a lfilm of sensitized material is capabie of being attached to receive the images or" the slits or holes in the periphery ont the drum.

Q. An apparatus for measuringv a short time, according to claim l, comprising a drum provided With slits or holes ot diiferent shapes, sizes, or arranged in zigzag' Way.

ln testimony `whereof We aiiix our signatures.

TAMOTSU AOKI. MASUO HAGIWARA. X 

